Collar positionable about a periphery of a contact pad and around a conductive structure secured to the contact pads, semiconductor device components including same, and methods for fabricating same

ABSTRACT

Dielectric collars are configured to be positioned laterally around contact pads of a semiconductor device or another substrate. Substrates on which the collars are positioned and that include contact pads that are exposed through the collars are also disclosed, as are methods for fabricating the collars and for positioning the collars on substrates. The collars may be positioned laterally adjacent to the contact pads of a substrate before or after conductive structures are secured to the contact pads. When the conductive structures are electrically connected to contact pads of another semiconductor device component, the collars prevent the material of the conductive structures from contacting regions of the surface of the substrate or other semiconductor device component that surround the contact pads. The collars may be pre-formed structures that are assembled with the substrate, or they may be formed on the substrate. A stereolithographic method of fabricating the collars is disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/590,418,filed Jun. 8, 2000, now U.S. Pat. No. 6,569,753, issued on May 27, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor devices havingcollars disposed about the peripheries of the contact pads thereof and,more specifically, to the use of stereolithography to fabricate suchcollars around the contact pads prior to securing conductive structuresto the contact pads. Particularly, the present invention pertains tocollars disposed about the peripheries of the contact pads of asemiconductor device component for enhancing the reliability ofconductive structures secured to the contact pads. The present inventionalso relates to semiconductor device components including such collars.

Reliability of Conductive Structures Used to Connect a SemiconductorDevice Face down to a Higher Level Substrate

2. State of the Art

Some types of semiconductor devices, such as flip-chip typesemiconductor dice, including ball grid array (BGA) packages andchip-scale packages (CSPs), can be connected to higher level substratesby orienting these semiconductor devices face down over the higher levelsubstrate. The contact pads of such semiconductor devices are typicallyconnected directly to corresponding contact pads of the higher levelsubstrate by solder balls or other discrete conductive elements.

Examples of materials that are known in the art to be useful inconnecting semiconductor devices face down to higher level substratesinclude, but are not limited to, lead-tin (Pb/Sn) solder, tin-silver(Sn/Ag) solder, tin-silver-nickel (Sn/Ag/Ni) solder, copper, gold, andconductive polymers. For example, 95/5 type Pb/Sn solder bumps (i.e.,solder having about 95% by weight lead and about 5% by weight tin) havebeen used in flip-chip, ball grid array, and chip-scale packaging typeattachments.

When 95/5 type Pb/Sn solder bumps are employed as conductive structuresto form a direct connection between a contact pad of a semiconductordevice and a contact pad of a higher level substrate, a quantity ofsolder paste, such as 63/37 type Pb/Sn solder, can be applied to thecontact pad of the higher level substrate to facilitate bonding of thesolder bump thereto. As the 95/5 type Pb/Sn solder and the 63/37 typePb/Sn solder are heated to bond the solder bump to a contact pad of thehigher level substrate, the 95/5 type Pb/Sn solder, which has a highermelting temperature than the 63/37 type Pb/Sn solder, softens when the63/37 type Pb/Sn solder is reflowed. When the 95/5 type Pb/Sn soldersoftens, the gravitational or compressive forces holding thesemiconductor device in position over the higher level substrate cancause the softened 95/5 type Pb/Sn solder bump to flatten, pushing thesolder laterally outward onto portions of the surface of thesemiconductor device that surround the contact pad to which the solderbump is secured and, in the case of fine pitch or spacing of balls, intothe solder of an adjacent ball.

Assemblies that include semiconductor devices connected face down tohigher level substrates using solder balls are subjected to thermalcycling during subsequent processing, burn-in, testing thereof, and innormal use. As these assemblies undergo thermal cycling, the solderballs thereof are also exposed to wide ranges of temperatures, causingthe solder balls to expand when heated and contract when cooled.Repeated variations in temperatures can cause solder fatigue, which canreduce the strength of the solder balls, cause the solder balls to fail,and diminish the reliability of the solder balls. The high temperaturesto which solder balls are exposed during burn-in and thermal cycling canalso soften and alter the conformations of the conductive structures.

The use of other conductive structures, which have more desirableshapes, such as pillars, or columns, and mushroom-type shapes, andconsume less conductive material than solder balls, to connectsemiconductor devices face down to higher level substrates has beenlimited since taller and thinner conductive structures may not retaintheir shapes upon being bonded to the contact pads of a higher levelsubstrate or in thermal cycling of the semiconductor device assembly.

The likelihood that a solder ball will be damaged by thermal cycling isparticularly high when the solder ball spreads over and contacts thesurface of the semiconductor device or the higher level substrate.Flattened solder balls and solder balls that contact regions of thesurface of a semiconductor device that surround the contact pads thereofare particularly susceptible to the types of damage that can be causedby thermal cycling of the semiconductor device.

In an attempt to increase the reliability with which solder ballsconnect semiconductor devices face down to higher level substrates,resins have been applied to semiconductor devices to form collars aroundthe bases of the solder balls protruding from the semiconductor devices.These resinous supports laterally contact the bases of the solder ballsto enhance the reliability thereof. The resinous supports are applied toa semiconductor device after solder balls have been secured to thecontact pads of the semiconductor device and before the semiconductordevice is connected face down to a higher level substrate. As those ofskill in the art are aware, however, the shapes of solder balls canchange when bonded to the contact pads of a substrate, particularlyafter reflow of the solder balls. If the shapes of the solder ballschange, the solder balls can fail to maintain contact with the resinoussupports, which could thereby fail to protect or enhance the reliabilityof the solder balls.

The use of solder balls in connecting a semiconductor device face downto higher level substrates is also somewhat undesirable from thestandpoint that, due to their generally spherical shapes, solder ballsconsume a great deal of area, or “real estate,” on a semiconductordevice. Thus, solder balls can limit the spacing between the adjacentcontact pads of a semiconductor device and, thus, the pitch of thecontact pads on the semiconductor device.

Moreover, when solder balls are reflowed, a phenomenon referred to as“outgassing” occurs, which can damage a semiconductor device proximateto the solder balls.

The inventors are not aware of any art that discloses peripheral collarsthat may be disposed individually around the contact pads of asemiconductor device so as to, at least in part, define the shapes ofconductive structures to be bonded to the contact pads or to facilitatebonding of a conductive structure to a bond pad without completelyreflowing the material of the conductive structures. Moreover, theinventors are not aware of methods that can be used to fabricate collarsaround either bare contact pads or contact pads having conductivestructures protruding therefrom.

Stereolithography

In the past decade, a manufacturing technique termed“stereolithography,” also known as “layered manufacturing,” has evolvedto a degree where it is employed in many industries.

Essentially, stereolithography, as conventionally practiced, involvesutilizing a computer to generate a three-dimensional (3-D) mathematicalsimulation or model of an object to be fabricated, such generationusually effected with 3-D computer-aided design (CAD) software. Themodel or simulation is mathematically separated or “sliced” into a largenumber of relatively thin, parallel, usually vertically superimposedlayers, each layer having defined boundaries and other featuresassociated with the model (and thus the actual object to be fabricated)at the level of that layer within the exterior boundaries of the object.A complete assembly or stack of all of the layers defines the entireobject and surface resolution of the object is, in part, dependent uponthe thickness of the layers.

The mathematical simulation or model is then employed to generate anactual object by building the object, layer by superimposed layer. Awide variety of approaches to stereolithography by different companieshas resulted in techniques for fabrication of objects from both metallicand nonmetallic materials. Regardless of the material employed tofabricate an object, stereolithographic techniques usually involvedisposition of a layer of unconsolidated or unfixed materialcorresponding to each layer within the object boundaries. This isfollowed by selective consolidation or fixation of the material to atleast a partially consolidated, or semisolid, state in those areas of agiven layer corresponding to portions of the object, the consolidated orfixed material also at that time being substantially concurrently bondedto a lower layer of the object to be fabricated. The unconsolidatedmaterial employed to build an object may be supplied in particulate orliquid form and the material itself may be consolidated or fixed, or aseparate binder material may be employed to bond material particles toone another and to those of a previously formed layer. In someinstances, thin sheets of material may be superimposed to build anobject, each sheet being fixed to a next lower sheet and unwantedportions of each sheet removed, a stack of such sheets defining thecompleted object. When particulate materials are employed, resolution ofobject surfaces is highly dependent upon particle size. When a liquid isemployed, surface resolution is highly dependent upon the minimumsurface area of the liquid which can be fixed and the minimum thicknessof a layer that can be generated. Of course, in either case, resolutionand accuracy of object reproduction from the CAD file is also dependentupon the ability of the apparatus used to fix the material to preciselytrack the mathematical instructions indicating solid areas andboundaries for each layer of material. Toward that end, and dependingupon the layer being fixed, various fixation approaches have beenemployed, including particle bombardment (electron beams), disposing abinder or other fixative (such as by ink-jet printing techniques), orirradiation using heat or specific wavelength ranges.

An early application of stereolithography was to enable rapidfabrication of molds and prototypes of objects from CAD files. Thus,either male or female forms on which mold material might be disposedmight be rapidly generated. Prototypes of objects might be built toverify the accuracy of the CAD file defining the object and to detectany design deficiencies and possible fabrication problems before adesign was committed to large-scale production.

In more recent years, stereolithography has been employed to develop andrefine object designs in relatively inexpensive materials and has alsobeen used to fabricate small quantities of objects where the cost ofconventional fabrication techniques is prohibitive for the same, such asin the case of plastic objects conventionally formed by injectionmolding. It is also known to employ stereolithography in the customfabrication of products generally built in small quantities or where aproduct design is rendered only once. Finally, it has been appreciatedin some industries that stereolithography provides a capability tofabricate products, such as those including closed interior chambers orconvoluted passageways, which cannot be fabricated satisfactorily usingconventional manufacturing techniques. It has also been recognized insome industries that a stereolithographic object or component may beformed or built around another, pre-existing object or component tocreate a larger product.

However, to the inventors' knowledge, stereolithography has yet to beapplied to mass production of articles in volumes of thousands ormillions, or employed to produce, augment or enhance products includingother, pre-existing components in large quantities, where minutecomponent sizes are involved, and where extremely high resolution and ahigh degree of reproducibility of results is required. In particular,the inventor is not aware of the use of stereolithography to fabricateperipheral collars around the contact pads of semiconductor devices,such as flip-chip type semiconductor devices or ball grid arraypackages. Furthermore, conventional stereolithography apparatus andmethods fail to address the difficulties of precisely locating andorienting a number of pre-existing components for stereolithographicapplication of material thereto without the use of mechanical alignmenttechniques or to otherwise assuring precise, repeatable placement ofcomponents.

SUMMARY OF THE INVENTION

The present invention includes a dielectric collar that surrounds theperiphery of a contact pad of a semiconductor device, semiconductordevice components including such collars, and methods for fabricatingthe collars. The present invention also includes forming conductivestructures of desired configurations with the collars, as well as othermethods for using the collars of the present invention.

A collar incorporating teachings of the present invention surrounds theperiphery of a contact pad exposed at the surface of a semiconductordevice component, such as a semiconductor die, a chip-scale packagesubstrate, or a carrier substrate. The collar protrudes from the surfaceof the semiconductor device component. If the collar is fabricatedbefore a conductive structure is secured to the contact pad, at least aportion of the surrounded contact pad is exposed through an aperturedefined by the collar. The aperture of the collar may be configured toimpart at least a base portion of a conductive structure to be bonded orotherwise secured to the contact pad with a desired shape anddimensions.

Conductive structures of any useful configuration can be used with ordefined by the collar of the present invention. Exemplary configurationsof conductive structures that can be used with or defined by the collarinclude, but are not limited to, balls, bumps, pillars or columns,mushroom shapes, or other shapes. These conductive structures can befabricated from solders, metals, metal alloys, conductor filled epoxies,conductive epoxies, and other conductive materials that are suitable foruse with semiconductor devices.

As the collar of the present invention facilitates the use of conductivestructures having shapes other than that of a solder ball, alternativelyshaped, thinner conductive structures can be spaced more closely,facilitating a decrease in the possible pitch of contact pads on asemiconductor device component. In addition, some alternativelyconfigured conductive structures, such as pillars and mushrooms, requireless material than balls.

Since the collar protrudes from the surface of the semiconductor devicecomponent, when a conductive structure is bonded or otherwise secured tothe contact pad exposed through the collar, the collar laterallysurrounds at least a portion of the conductive structure. Accordingly,when a conductive structure is formed on or secured to a contact pad, orduring bonding of the conductive structure to the contact pad of anotherdevice or substrate, the contact pad collar of the present inventionlaterally contains at least a base portion of a conductive structureextending therethrough and prevents the material of the conductivestructure from contacting and wetting portions of the surface of thesemiconductor device component adjacent to the contact pad.

The collar is preferably configured to contact a conductive structureextending therethrough so as to laterally support and protect at leastthe contacted portion of the conductive structure during thermal cyclingof the semiconductor device, such as in the repeated use thereof.

In addition, use of collars according to the present invention, whichmay be of substantial height or protrusion from a substrate so as toencompass the conductive structures at or approaching their heights, mayeliminate the need for an insulative underfill conventionally appliedbetween a die and a higher level substrate.

Another significant advantage of the collars of the present invention isthe containment of the conductive material of the conductive structures,in the manner of a dam, during connection of a semiconductor device facedown upon a higher level substrate, thus preventing contamination orwetting of the passivation layer surrounding the contact pads.

According to another aspect, the present invention includes a method forfabricating the collar. In a preferred embodiment of the method, acomputer-controlled, 3-D CAD-initiated process known as“stereolithography” or “layered manufacturing” is used to fabricate thecollar. When stereolithographic processes are employed, each collar isformed as either a single layer or a series of superimposed, contiguous,mutually adhered layers of material.

The stereolithographic method of fabricating the collars of the presentinvention preferably includes the use of a machine vision system tolocate the semiconductor devices or other substrates on which thecollars are to be fabricated, as well as the features or othercomponents on or associated with the semiconductor devices or othersubstrates (e.g., solder bumps, contact pads, conductor traces, etc.).The use of a machine vision system directs the alignment of astereolithography system with each semiconductor device or othersubstrate for material disposition purposes. Accordingly, thesemiconductor devices or other substrates need not be preciselymechanically aligned with any component of the stereolithography systemto practice the stereolithographic embodiment of the method of thepresent invention.

In a preferred embodiment, the collars to be fabricated upon orpositioned upon and secured to a semiconductor device component inaccordance with the invention are fabricated using precisely focusedelectromagnetic radiation in the form of an ultraviolet (UV) wavelengthlaser under control of a computer and responsive to input from a machinevision system, such as a pattern recognition system, to fix or cureselected regions of a layer of a liquid photopolymer material disposedon the semiconductor device or other substrate.

The collars of the present invention may be fabricated around thecontact pads of the semiconductor device component either before orafter conductive structures are bonded or otherwise secured to thecontact pads, although it is preferred that the collars be fabricatedbefore securing the conductive structures to the contact pads.

Other features and advantages of the present invention will becomeapparent to those of skill in the art through consideration of theensuing description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate exemplary embodiments of theinvention, wherein some dimensions may be exaggerated for the sake ofclarity, and wherein:

FIG. 1 is an enlarged perspective view of a semiconductor device havingcollars positioned around the exposed contact pads thereof;

FIG. 2 is a cross-section taken along line 2—2 of FIG. 1, depicting theapertures of the collars;

FIG. 3 is a cross-sectional view illustrating the face down connectionof the semiconductor device of FIGS. 1 and 2 to a higher levelsubstrate;

FIG. 4 is an enlarged perspective view of another semiconductor devicehaving collars positioned around the contact pads thereof, each collarlaterally surrounding a portion of a conductive structure bonded to thesurrounded contact pad;

FIG. 5 is a cross-section taken along line 5—5 of FIG. 4, depictingconductive structures extending through and laterally supported by thecollars;

FIG. 6 is a cross-sectional view illustrating the face down connectionof the semiconductor device of FIGS. 4 and 5 to a higher levelsubstrate;

FIG. 7 is a cross-sectional view illustrating a collar protruding thesubstantial distance of a pillar-shaped conductive structure extendingtherethrough;

FIG. 8 is a perspective view of a portion of a wafer having a pluralityof semiconductor devices thereon, depicting collars being fabricatedaround each of the contact pads of the semiconductor devices at thewafer level;

FIG. 9 is a schematic representation of an exemplary stereolithographyapparatus that can be employed in the method of the present invention tofabricate the collars of the present invention; and

FIG.10 is a partial cross-sectional side view of a semiconductor devicedisposed on a platform of a stereolithographic apparatus for theformation of collars around the contact pads of the semiconductordevice.

DETAILED DESCRIPTION OF THE INVENTION Collars

With reference to FIGS. 1 and 2, a semiconductor device 10 havingcontact pads 12 on a surface 14 thereof is illustrated. Semiconductordevice 10 can be a semiconductor die, a chip-scale package, a ball gridarray package, a carrier substrate, or any other type of semiconductordevice component having contact pads to which conductive structures,such as balls, bumps, or pillars, can be attached.

As illustrated, a collar 50 surrounds the periphery of each contact pad12. Each collar 50 has an aperture 52, through which at least a portionof the surrounded contact pad 12 is exposed. Each collar 50 protrudesfrom surface 14 of semiconductor device 10 so as to laterally surroundat least a portion of a conductive structure to be bonded or otherwisesecured to contact pad 12 and to prevent the material of a conductivestructure from contacting portions of surface 14 adjacent to contact pad12.

Referring now to FIG. 3, semiconductor device 10 is shown in a face downorientation over a higher level substrate 30. Substrate 30 has contactpads 32, or terminals, exposed at a surface 34 thereof. Contact pads 32are preferably arranged so as to align with corresponding ones ofcontact pads 12 upon positioning semiconductor device 10 face down oversubstrate 30. Each contact pad 12 of semiconductor device 10 iselectrically connected to its corresponding contact pad 32 of substrate30 by way of a conductive structure 20, such as a bump, ball, or pillar,formed from a conductive material, such as a solder, other metal ormetal alloy, a conductor filled epoxy, or a conductive epoxy.

As will be explained in greater detail below, collars 50 are at leastpartially fabricated prior to connecting conductive structures 20 tocontact pads 12. As depicted in FIG. 3, a base portion 22 of eachconductive structure 20, which is bonded or otherwise secured to thecontact pad 12 exposed through aperture 52 of collar 50, has a shapethat is complementary to the configuration of aperture 52. Thus, eachcollar 50 contacts the conductive structure 20 that extends throughaperture 52. Base portion 22 of each conductive structure 20 can have ashape that is defined by aperture 52 or that is configuredcomplementarily to aperture 52. Accordingly, collars 50 and theapertures 52 thereof can be configured to impart desired shapes anddimensions to conductive structures 20 or at least base portion 22thereof.

Alternatively, conductive structures 20 can have base portions 22 thatare not shaped complementarily to apertures 52 or that extend throughapertures 52 without contacting collars 50.

With continued reference to FIG. 3, semiconductor device 10 is connectedface down to a higher level substrate 30, such as a carrier substrate.Conductive structures 20 connect contact pads 12 of semiconductor device10 to corresponding contact pads 32 exposed at surface 34 of substrate30. As conductive structures 20 are being bonded or otherwise secured tocontact pads 32, collar 50 prevents material of conductive structures 20from contacting regions of surface 14 adjacent to contact pads 12.Moreover, collars 50 contact conductive structures 20 so as to laterallysupport and protect at least the contacted portions of conductivestructures 20.

FIGS. 4 and 5 illustrate another semiconductor device 10, which hasconductive structures 20′, shown as solder bumps, protruding from eachof the contact pads 12 on the surface 14 thereof. The portion of eachconductive structure 20′ adjacent surface 14 and the periphery of eachcontact pad 12 is laterally surrounded by another embodiment of collar50′, which protrudes from surface 14.

As shown in FIG. 5, conductive structure 20′ extends through an aperture52′ of collar 50′ to contact pad 12. Collar 50′ contacts the sides of abase portion 22′ of conductive structure 20′ that extends throughaperture 52′. FIG. 5 also depicts portions of collar 50′ located beneathconductive structure 20′. These portions of collar 50′ are referred toherein as “shadowed” areas 54′.

Turning now to FIG. 6, semiconductor device 10 is depicted as beinginvertedly disposed over and connected to a higher level substrate 30.Conductive structures 20′ connect each contact pad 12 of semiconductordevice 10 to a corresponding contact pad 32 exposed at a surface 34 ofsubstrate 30. As depicted, collars 50′ prevent material of conductivestructures 20′ from contacting surface 14 of semiconductor device 10.

As shown in FIG. 7, a collar 50″ can also protrude from surface 14substantially the same distance as a pillar-shaped conductive structure20″ secured to contact pad 12. When such a collar 50″ is fabricatedaround contact pad 12 before conductive structure 20″ is securedthereto, conductive structure 20″ can be formed by disposing a quantityof conductive material, such as a solder, metal, metal alloy, conductorfilled epoxy, or conductive elastomer, into aperture 52″. Alternatively,a pre-formed conductive structure 20″ can be secured to contact pad 12and collar 50″ fabricated around conductive structure 20″.

It should also be noted that conductive structures 20 (see FIGS. 2 and3), 20″ are thinner than conductive structures 20′ (see FIGS. 4-6).Thus, conductive structures 20, 20″ consume less area, or real estate,on semiconductor device 10 than conductive structures 20′. Accordingly,conductive structures 20, 20″ are spaced farther apart than conductivestructures 20′. Furthermore, conductive structures 20, 20″ can be usedwith semiconductor devices having tighter, or smaller, pitches than thepitches of semiconductor devices with which solder balls or similarconductive structures 20′ are used. As conductive structures 20, 20″ arethinner than solder balls, such as conductive structure 20′, conductivestructures 20, 20″ also consume less conductive material than conductivestructures 20′.

FIG. 8 illustrates collars 50 on semiconductor devices 10, in this casesemiconductor dice, that have yet to be singulated, or diced, from awafer 72 or from a portion of a wafer 72. Each semiconductor device 10on wafer 72 is separated from adjacent semiconductor devices 10 by astreet 74 on surface 14.

While collars 50, 50′, 50″ are preferably substantially simultaneouslyfabricated on or secured to a collection of semiconductor devices 10,such as prior to singulating semiconductor dice from a wafer 72, collars50, 50′, 50″ can also be fabricated on or secured to collections ofindividual semiconductor devices 10 or other substrates, or toindividual semiconductor devices 10 or other substrates, such assubstrate 30. As another alternative, collars 50, 50′, 50″ can besubstantially simultaneously fabricated on or secured to a collection ofmore than one type of semiconductor device 10 or other substrate.

Collars 50, 50′, 50″ can be fabricated directly on semiconductor devices10. Alternatively, collars 50, 50′, 50″ can be fabricated separatelyfrom semiconductor devices 10, then secured thereto as known in the art,such as by the use of a suitable adhesive.

Collars 50, 50′, 50″ are preferably fabricated from a photo-curablepolymer, or “photopolymer” by stereolithographic processes. Whenfabricated directly on a semiconductor device 10, collars 50, 50′, 50″can be made either before or after conductive structures 20, 20′, 20″are connected to contact pads 12 of semiconductor device 10.

For simplicity, the ensuing description is limited to an explanation ofa method of fabricating collars 50 on a semiconductor device 10 prior tosecuring conductive structures 20 to contact pads 12 of semiconductordevice 10. As should be appreciated by those of skill in the art,however, the method described herein is also useful for fabricatingcollars 50′, 50″ on semiconductor device 10, as well as for fabricatingcollars 50, 50′, 50″ on one or more semiconductor devices 10 or othersubstrates having conductive structures 20, 20′, 20″ already secured tothe contact pads 12 thereof.

Stereolithography Apparatus and Methods

FIG. 9 schematically depicts various components and operation of anexemplary stereolithography apparatus 80 to facilitate the reader'sunderstanding of the technology employed in implementation of the methodof the present invention, although those of ordinary skill in the artwill understand and appreciate that apparatus of other designs andmanufacture may be employed in practicing the method of the presentinvention. The preferred, basic stereolithography apparatus forimplementation of the method of the present invention, as well asoperation of such apparatus, are described in great detail in UnitedStates Patents assigned to 3-D Systems, Inc., of Valencia, Calif., suchpatents including, without limitation, U.S. Pat. Nos. 4,575,330;4,929,402; 4,996,010; 4,999,143; 5,015,424; 5,058,988; 5,059,021;5,059,359; 5,071,337; 5,076,974; 5,096,530; 5,104,592; 5,123,734;5,130,064; 5,133,987; 5,141,680; 5,143,663; 5,164,128; 5,174,931;5,174,943; 5,182,055; 5,182,056; 5,182,715; 5,184,307; 5,192,469;5,192,559; 5,209,878; 5,234,636; 5,236,637; 5,238,639; 5,248,456;5,256,340; 5,258,146; 5,267,013; 5,273,691; 5,321,622; 5,344,298;5,345,391; 5,358,673; 5,447,822; 5,481,470; 5,495,328; 5,501,824;5,554,336; 5,556,590; 5,569,349; 5,569,431; 5,571,471; 5,573,722;5,609,812; 5,609,813; 5,610,824; 5,630,981; 5,637,169; 5,651,934;5,667,820; 5,672,312; 5,676,904; 5,688,464; 5,693,144; 5,695,707;5,711,911; 5,776,409; 5,779,967; 5,814,265; 5,850,239; 5,854,748;5,855,718; 5,855,836; 5,885,511; 5,897,825; 5,902,537; 5,902,538;5,904,889; 5,943,235; and 5,945,058. The disclosure of each of theforegoing patents is hereby incorporated herein by this reference.

With continued reference to FIG. 9 and as noted above, a 3-D CAD drawingof an object to be fabricated in the form of a data file is placed inthe memory of a computer 82 controlling the operation of apparatus 80 ifcomputer 82 is not a CAD computer in which the original object design iseffected. In other words, an object design may be effected in a firstcomputer in an engineering or research facility and the data filestransferred via wide or local area network, tape, disc, CD-ROM, orotherwise, as known in the art, to computer 82 of apparatus 80 forobject fabrication.

The data is preferably formatted in an STL (for STereoLithography) file,STL being a standardized format employed by a majority of manufacturersof stereolithography equipment. Fortunately, the format has been adoptedfor use in many solid-modeling CAD programs, so translation from anotherinternal geometric database format is often unnecessary. In an STL file,the boundary surfaces of an object are defined as a mesh ofinterconnected triangles.

Apparatus 80 also includes a reservoir 84 (which may comprise aremovable reservoir interchangeable with others containing differentmaterials) of an unconsolidated material 86 to be employed infabricating the intended object. In the currently preferred embodiment,the unconsolidated material 86 is a liquid, photo-curable polymer, or“photopolymer,” that cures in response to light in the UV wavelengthrange. The surface level 88 of material 86 is automatically maintainedat an extremely precise, constant magnitude by devices known in the artresponsive to output of sensors within apparatus 80 and preferably undercontrol of computer 82. A support platform or elevator 90, preciselyvertically movable in fine, repeatable increments in direction 116responsive to control of computer 82, is located for movement downwardinto and upward out of material 86 in reservoir 84.

An object may be fabricated directly on platform 90 or on a substratedisposed on platform 90. When the object is to be fabricated on asubstrate disposed on platform 90, the substrate may be positioned onplatform 90 and secured thereto by way of one or more base supports 122(see FIG. 10). Such base supports 122 may be fabricated before orsimultaneously with the stereolithographic fabrication of one or moreobjects on platform 90 or a substrate disposed thereon. These supports122 may support, or prevent lateral movement of, the substrate relativeto a surface 100 of platform 90. Supports 122 may also provide aperfectly horizontal reference plane for fabrication of one or moreobjects thereon, as well as facilitate the removal of a substrate fromplatform 90 following the stereolithographic fabrication of one or moreobjects on the substrate. Moreover, where a so-called “recoater” blade102 is employed to form a layer of material on platform 90 or asubstrate disposed thereon, supports 122 can preclude inadvertentcontact of recoater blade 102, to be described in greater detail below,with surface 100 of platform 90.

Apparatus 80 has a UV wavelength range laser plus associated optics andgalvanometers (collectively identified as laser 92) for controlling thescan of laser beam 96 in the X-Y plane across platform 90. Laser 92 hasassociated therewith a mirror 94 to reflect beam 96 downwardly as beam98 toward surface 100 of platform 90. Beam 98 is traversed in a selectedpattern in the X-Y plane, that is to say, in a plane parallel to surface100, by initiation of the galvanometers under control of computer 82 toat least partially cure, by impingement thereon, selected portions ofmaterial 86 disposed over surface 100 to at least a partiallyconsolidated (e.g., semisolid) state. The use of mirror 94 lengthens thepath of the laser beam, effectively doubling the same, and provides amore vertical beam 98 than would be possible if the laser 92 itself weremounted directly above platform surface 100, thus enhancing resolution.

Referring now to FIGS. 9 and 10, data from the STL files resident incomputer 82 is manipulated to build an object, such as collar 50,illustrated in FIGS. 1-3 and 8, or base supports 122, one layer at atime. Accordingly, the data mathematically representing one or more ofthe objects to be fabricated are divided into subsets, each subsetrepresenting a slice or layer of the object. The division of data iseffected by mathematically sectioning the 3-D CAD model into at leastone layer, a single layer or a “stack” of such layers representing theobject. Each slice may be from about 0.0001 to about 0.0300 inch thick.As mentioned previously, a thinner slice promotes higher resolution byenabling better reproduction of fine vertical surface features of theobject or objects to be fabricated.

When one or more base supports 122 are to be stereolithographicallyfabricated, supports 122 may be programmed as a separate STL file fromthe other objects to be fabricated. The primary STL file for the objector objects to be fabricated and the STL file for base support(s) 122 aremerged.

Before fabrication of a first layer for a support 122 or an object to befabricated is commenced, the operational parameters for apparatus 80 areset to adjust the size (diameter if circular) of the laser light beamused to cure material 86. In addition, computer 82 automatically checksand, if necessary, adjusts by means known in the art, the surface level88 of material 86 in reservoir 84 to maintain the same at an appropriatefocal length for laser beam 98. U.S. Pat. No. 5,174,931, referencedabove and previously incorporated herein by reference, discloses onesuitable level control system. Alternatively, the height of mirror 94may be adjusted responsive to a detected surface level 88 to cause thefocal point of laser beam 98 to be located precisely at the surface ofmaterial 86 at surface level 88 if level 88 is permitted to vary,although this approach is more complex. Platform 90 may then besubmerged in material 86 in reservoir 84 to a depth 87 equal to thethickness of one layer or slice of the object to be formed, and theliquid surface level 88 is readjusted as required to accommodatematerial 86 displaced by submergence of platform 90. Laser 92 is thenactivated so laser beam 98 will scan unconsolidated (e.g., liquid orpowdered) material 86 disposed over surface 100 of platform 90 to atleast partially consolidate (e.g., polymerize to at least a semisolidstate) material 86 at selected locations, defining the boundaries of afirst layer 122A of base support 122 and filling in solid portionsthereof. Platform 90 is then lowered by a distance equal to thickness ofsecond layer 122B and laser beam 98 scanned over selected regions of thesurface of material 86 to define and fill in the second layer whilesimultaneously bonding the second layer to the first. The process maythen be repeated as often as necessary, layer by layer, until basesupport 122 is completed. Platform 90 is then moved relative to mirror94 to form any additional base supports 122 on platform 90 or asubstrate disposed thereon or to fabricate objects upon platform 90,base support 122, or a substrate, as provided in the control software.The number of layers required to erect support 122 or one or more otherobjects to be formed depends upon the height of the object or objects tobe formed and the desired layer thickness 108, 110. The layers of astereolithographically fabricated structure with a plurality of layersmay have different thicknesses.

If a recoater blade 102 is employed, the process sequence is somewhatdifferent. In this instance, surface 100 of platform 90 is lowered intounconsolidated (e.g., liquid) material 86 below surface level 88 adistance greater than a thickness of a single layer of material 86 to becured, then raised above surface level 88 until platform 90, a substratedisposed thereon, or a structure being formed on platform 90 or asubstrate thereon is precisely one layer's thickness below blade 102.Blade 102 then sweeps horizontally over platform 90 or (to save time) atleast over a portion thereof on which one or more objects are to befabricated to remove excess material 86 and leave a film of preciselythe desired thickness. Platform 90 is then lowered so that the surfaceof the film and material level 88 are coplanar and the surface of theunconsolidated material 86 is still. Laser 92 is then initiated to scanwith laser beam 98 and define the first layer 130A. The process isrepeated, layer by layer, to define each succeeding layer 130B andsimultaneously bond the same to the next lower layer 130A until all ofthe layers of the object or objects to be fabricated are completed. Amore detailed discussion of this sequence and apparatus for performingthe same is disclosed in U.S. Pat. No. 5,174,931, previouslyincorporated herein by reference.

As an alternative to the above approach to preparing a layer of material86 for scanning with laser beam 98, a layer of unconsolidated (e.g.,liquid) material 86 may be formed on surface 100 of support platform 90,on a substrate disposed on platform 90, or on one or more objects beingfabricated by lowering platform 90 to flood material 86 over surface100, over a substrate disposed thereon, or over the highest completedlayer of the object or objects being formed, then raising platform 90and horizontally traversing a so-called “meniscus” blade horizontallyover platform 90 to form a layer of unconsolidated material having thedesired thickness over platform 90, the substrate, or each of theobjects being formed. Laser 92 is then initiated and a laser beam 98scanned over the layer of unconsolidated material to define at least theboundaries of the solid regions of the next higher layer of the objector objects being fabricated.

Yet another alternative to layer preparation of unconsolidated (e.g.,liquid) material 86 is to merely lower platform 90 to a depth equal tothat of a layer of material 86 to be scanned, and to then traverse acombination flood bar and meniscus bar assembly horizontally overplatform 90, a substrate disposed on platform 90, or one or more objectsbeing formed to substantially concurrently flood material 86 thereoverand to define a precise layer thickness of material 86 for scanning.

All of the foregoing approaches to liquid material flooding and layerdefinition and apparatus for initiation thereof are known in the art andare not material to the practice of the present invention, therefore, nofurther details relating thereto will be provided herein.

In practicing the present invention, a commercially availablestereolithography apparatus operating generally in the manner as thatdescribed above with respect to apparatus 80 of FIG. 9 is preferablyemployed, but with further additions and modifications as hereinafterdescribed for practicing the method of the present invention. Forexample and not by way of limitation, the SLA-250/50HR, SLA-5000 andSLA-7000 stereolithography systems, each offered by 3-D Systems, Inc.,of Valencia, Calif., are suitable for modification. Photopolymersbelieved to be suitable for use in practicing the present inventioninclude Cibatool SL 5170 and SL 5210 resins for the SLA-250/50HR system,Cibatool SL 5530 resin for the SLA-5000 and 7000 systems, and CibatoolSL 7510 resin for the SLA-7000 system. All of these photopolymers areavailable from Ciba Specialty Chemicals Inc.

By way of example and not limitation, the layer thickness 87 of material86 to be formed, for purposes of the invention, may be on the order ofabout 0.0001 to 0.0300 inch, with a high degree of uniformity. It shouldbe noted that different material layers may have different heights so asto form a structure of a precise, intended total height or to providedifferent material thicknesses for different portions of the structure.The size of the laser beam “spot” impinging on the surface of material86 to cure the same may be on the order of 0.001 inch to 0.008 inch.Resolution is preferably ±0.0003 inch in the X-Y plane (parallel tosurface 100) over at least a 0.5 inch×0.25 inch field from a centerpoint, permitting a high resolution scan effectively across a 1.0inch×0.5 inch area. Of course, it is desirable to have substantiallythis high a resolution across the entirety of surface 100 of platform 90to be scanned by laser beam 98, such area being termed the “field ofexposure,” and being substantially coextensive with the vision field ofa machine vision system employed in the apparatus of the invention asexplained in more detail below. The longer and more effectively verticalthe path of laser beam 96/98, the greater the achievable resolution.

Referring again to FIG. 9, it should be noted that apparatus 80 usefulin the method of the present invention includes a camera 140 which is incommunication with computer 82 and preferably located, as shown, inclose proximity to optics and mirror 94 located above surface 100 ofsupport platform 90. Camera 140 may be any one of a number ofcommercially available cameras, such as capacitive-coupled discharge(CCD) cameras available from a number of vendors. Suitable circuitry asrequired for adapting the output of camera 140 for use by computer 82may be incorporated in a board 142 installed in computer 82, which isprogrammed, as known in the art, to respond to images generated bycamera 140 and processed by board 142. Camera 140 and board 142 maytogether comprise a so-called “machine vision system” and, specifically,a “pattern recognition system” (PRS), operation of which will bedescribed briefly below for a better understanding of the presentinvention. Alternatively, a self-contained machine vision systemavailable from a commercial vendor of such equipment may be employed.For example, and without limitation, such systems are available fromCognex Corporation of Natick, Mass. For example, the apparatus of theCognex BGA Inspection Package™ or the SMD Placement Guidance Package™may be adapted to the present invention, although it is believed thatthe MVS-8000™ product family and the Checkpoint® product line, thelatter employed in combination with Cognex PatMax™ software, may beespecially suitable for use in the present invention.

It is noted that a variety of machine vision systems are in existence,examples of which and their various structures and uses are described,without limitation, in U.S. Pat. Nos. 4,526,646; 4,543,659; 4,736,437;4,899,921; 5,059,559; 5,113,565; 5,145,099; 5,238,174; 5,463,227;5,288,698; 5,471,310; 5,506,684; 5,516,023; 5,516,026; and 5,644,245.The disclosure of each of the immediately foregoing patents is herebyincorporated by this reference.

Stereolithographic Fabrication of the Collars

In order to facilitate fabrication of one or more collars 50 inaccordance with the method of the present invention with apparatus 80, adata file representative of the size, configuration, thickness andsurface topography of, for example, a particular type and design ofsemiconductor device 10 or other substrate upon which one or morecollars 50 are to be mounted, is placed in the memory of computer 82.Also, if it is desired that the collars 50 be so positioned onsemiconductor device 10 taking into consideration features of a higherlevel substrate 30 (see FIG. 3) to which semiconductor device 10 is tobe connected, a data file representative of substrate 30 and thefeatures thereof may be placed in memory.

One or more semiconductor devices 10, wafers 72 (see FIG. 8), or othersubstrates may be placed on surface 100 of platform 90 for fabricationof collars 50 around contact pads 12 thereof. If one or moresemiconductor devices 10, wafers 72, or other substrates are to be heldon or supported above platform 90 by stereolithographically formed basesupports 122, one or more layers of material 86 are sequentiallydisposed on surface 100 and selectively altered by use of laser 92 toform base supports 122.

Camera 140 is then activated to locate the position and orientation ofeach semiconductor device 10, including those on a wafer 72 (see FIG.8), or other substrate upon which collars 50 are to be fabricated. Thefeatures of each semiconductor device 10, wafer 72, or other substrateare compared with those in the data file residing in memory, thelocational and orientational data for each semiconductor device 10,wafer 72, or other substrate then also being stored in memory. It shouldbe noted that the data file representing the design, size, shape andtopography for each semiconductor device 10 or other substrate may beused at this juncture to detect physically defective or damagedsemiconductor devices 10 or other substrates prior to fabricatingcollars 50 thereon or before conducting further processing or assemblyof semiconductor device 10 or other substrates. Accordingly, suchdamaged or defective semiconductor devices 10 or other substrates can bedeleted from the process of fabricating collars 50, from furtherprocessing, or from assembly with other components. It should also benoted that data files for more than one type (size, thickness,configuration, surface topography) of each semiconductor device 10 orother substrate may be placed in computer memory and computer 82programmed to recognize not only the locations and orientations of eachsemiconductor device 10 or other substrate, but also the type ofsemiconductor device 10 or other substrate at each location uponplatform 90 so that material 86 may be at least partially consolidatedby laser beam 98 in the correct pattern and to the height required todefine collars 50 in the appropriate, desired locations on eachsemiconductor device 10 or other substrate.

Continuing with reference to FIGS. 9 and 10, wafer 72 or the one or moresemiconductor devices 10 or other substrates on platform 90 may then besubmerged partially below the surface level 88 of liquid material 86 toa depth greater than the thickness of a first layer of material 86 to beat least partially consolidated (e.g., cured to at least a semisolidstate) to form the lowest layer 130A of each collar 50 at theappropriate location or locations on each semiconductor device 10 orother substrate, then raised to a depth equal to the layer thickness,surface level 88 of material 86 being allowed to become calm.Photopolymers that are useful as material 86 exhibit a desirabledielectric constant, are of sufficient (i.e., semiconductor grade)purity, exhibit good adherence to other semiconductor device materials,and have a similar coefficient of thermal expansion (CTE) to thematerial of conductive structures 20 (FIG. 3) (e.g., solder or othermetal or metal alloy, or conductive or conductor filled epoxy).Preferably, the CTE of material 86 is sufficiently similar to that ofconductive structures 20 to prevent undue stressing thereof duringthermal cycling of semiconductor device 10 or another substrate intesting, subsequent processing, and subsequent normal operation.Exemplary photopolymers exhibiting these properties are believed toinclude, but are not limited to, the above-referenced resins from CibaSpecialty Chemical Inc. One particular concern in determining resinsuitability is the substantial absence of mobile ions, specificallyfluorides.

Laser 92 is then activated and scanned to direct beam 98, under controlof computer 82, toward specific locations of surface level 88 relativeto each semiconductor device 10 or other substrate to effect theaforementioned partial cure of material 86 to form a first layer 50A ofeach collar 50. Platform 90 is then lowered into reservoir 84 and raiseda distance equal to the desired thickness of another layer 50B of eachcollar 50 and laser 92 is activated to add another layer 50B to eachcollar 50 under construction. This sequence continues, layer by layer,until each of the layers of collars 50 have been completed.

In FIG. 10, the first layer of collar 50 is identified by numeral 50Aand the second layer is identified by numeral 50B. Likewise, the firstlayer of base support 122 is identified by numeral 122A and the secondlayer thereof is identified by numeral 122B. As illustrated, both basesupport 122 and collar 50 have only two layers. Collars 50 with anynumber of layers are, however, within the scope of the presentinvention. The use of a large number of layers may be employed tosubstantially simulate the shape of the outer surface of a conductivestructure to be encompassed by collar 50.

Each layer 50A, 50B of collar 50 is preferably built by first definingany internal and external object boundaries of that layer with laserbeam 98, then hatching solid areas of collar 50 located within theobject boundaries with laser beam 98. An internal boundary of a layermay comprise aperture 52, a through-hole, a void, or a recess in collar50, for example. If a particular layer includes a boundary of a void inthe object above or below that layer, then laser beam 98 is scanned in aseries of closely-spaced, parallel vectors so as to develop a continuoussurface, or skin, with improved strength and resolution. The time ittakes to form each layer depends upon the geometry thereof, the surfacetension and viscosity of material 86, and the thickness of that layer.

Alternatively, collars 50 may each be formed as a partially cured outerskin extending above surface 14 of semiconductor device 10 and forming adam within which unconsolidated material 86 can be contained. This maybe particularly useful where the collars 50 protrude a relatively highdistance 56 from surface 14. In this instance, support platform 90 maybe submerged so that material 86 enters the area within the dam, raisedabove surface level 88, and then laser beam 98 activated and scanned toat least partially cure material 86 residing within the dam or,alternatively, to merely cure a “skin” comprising the contact surfaceaperture 52, a final cure of the material of the collars 50 beingeffected subsequently by broad-source UV radiation in a chamber or bythermal cure in an oven. In this manner, collars 50 of extremely precisedimensions may be formed of material 86 by apparatus 80 in minimal time.

When collars 50′, depicted in FIGS. 4-6, are being fabricated on asubstrate, such as semiconductor device 10, having conductive structures20′ already secured to the contact pads 12 thereof, some of material 86may be located in shadowed areas 54′ (see FIGS. 5 and 6) lying underportions of a conductive structure 20′. As laser beam 98 is directedsubstantially vertically downwardly toward surface level 88 of material86, material 86 located in shadowed regions 54′ will not be contacted oraltered by laser beam 98. Nonetheless, the unconsolidated material 86 inshadowed areas 54′ will become trapped therein as material 86 adjacentto, and laterally outward from, shadowed areas 54′ is at least partiallyconsolidated as collar 50′ is built up around conductive structure 20′.Such trapped, unconsolidated material 86 will eventually cure due to thecross-linking initiated in the outwardly adjacent photopolymer and thecure can be subsequently accelerated as known in the art, such as by athermal cure.

Once collars 50, or at least the outer skins thereof, have beenfabricated, platform 90 is elevated above surface level 88 of material86 and platform 90 is removed from apparatus 80, along with anysubstrate (e.g., semiconductor device 10, wafer 72 (see FIG. 8), orother substrate) disposed thereon and any stereolithographicallyfabricated structures, such as collars 50. Excess, unconsolidatedmaterial 86 (e.g., excess uncured liquid) may be manually removed fromplatform 90, from any substrate disposed thereon, and from collars 50.Each semiconductor device 10, wafer 72, or other substrate is removedfrom platform 90, such as by cutting the substrate free of base supports122. Alternatively, base supports 122 may be configured to readilyrelease semiconductor devices 10, wafers 72, or other substrates. Asanother alternative, a solvent may be employed to release base supports122 from platform 90. Such release and solvent materials are known inthe art. See, for example, U.S. Pat. No. 5,447,822 referenced above andpreviously incorporated herein by reference.

Collars 50 and semiconductor device 10 may also be cleaned by use ofknown solvents that will not substantially degrade, deform, or damagecollars 50 or a substrate to which collars 50 are secured.

As noted previously, collars 50 may then require postcuring. Collars 50may have regions of unconsolidated material contained within a boundaryor skin thereof or in a shadowed area 54′ (see FIGS. 5 and 6), ormaterial 86 may be only partially consolidated (e.g., polymerized orcured) and exhibit only a portion (typically 40% to 60%) of its fullyconsolidated strength. Postcuring to completely harden collars 50 may beeffected in another apparatus projecting UV radiation in a continuousmanner over collars 50 or by thermal completion of the initial,UV-initiated partial cure.

It should be noted that the height, shape, or placement of each collar50 on each specific semiconductor device 10 or other substrate may vary,again responsive to output of camera 140 or one or more additionalcameras 144, 146, or 148, shown in broken lines, detecting theprotrusion of unusually high (or low) preplaced conductive structureswhich could affect the desired distance 56 that collars 50 will protrudefrom surface 14. Likewise, the lateral extent (e.g., diameter) of eachpreplaced conductive structure may be recognized and the girth of theouter boundary of each collar 50 adjusted accordingly. In any case,laser 92 is again activated to at least partially cure material 86residing on each semiconductor device 10 or other substrate to form thelayer or layers of each collar 50.

Although FIGS. 9 and 10 illustrate the stereolithographic fabrication ofcollars 50 on a substrate, such as a semiconductor device 10, a wafer 72(FIG. 8), or another substrate, including a plurality of semiconductordevices 10 or other substrates, collars 50 can be fabricated separatelyfrom a substrate, then secured to a substrate, by known processes, suchas by the use of a suitable adhesive material.

The use of a stereolithographic process as exemplified above tofabricate collars 50 is particularly advantageous since a large numberof collars 50 may be fabricated in a short time, the collar height andposition are computer controlled to be extremely precise, wastage ofunconsolidated material 86 is minimal, solder coverage of passivationmaterials is avoided, and the stereolithography method requires minimalhandling of semiconductor devices 10, wafers 72, or other substrates.

Stereolithography is also an advantageous method of fabricating collars50 according to the present invention since stereolithography can beconducted at substantially ambient temperature, the small spot size andrapid traverse of laser beam 98 resulting in negligible thermal stressupon semiconductor devices 10, wafers 72, or other substrates, as wellas on the features thereof.

The stereolithography fabrication process may also advantageously beconducted at the wafer level or on multiple substrates, savingfabrication time and expense. As the stereolithography method of thepresent invention recognizes specific semiconductor devices 10 or othersubstrates 30, variations between individual substrates areaccommodated. Accordingly, when the stereolithography method of thepresent invention is employed, collars 50 can be simultaneouslyfabricated on different types of semiconductor devices 10 or othersubstrates, as well as on both semiconductor devices 10 and othersubstrates.

While the present invention has been disclosed in terms of certainpreferred embodiments, those of ordinary skill in the art will recognizeand appreciate that the invention is not so limited. Additions,deletions and modifications to the disclosed embodiments may be effectedwithout departing from the scope of the invention as claimed herein.Similarly, features from one embodiment may be combined with those ofanother while remaining within the scope of the invention.

1. A collar positionable around a contact pad of a semiconductor device,the collar including an aperture to which at least a portion of thecontact pad is exposed, the collar comprising a plurality ofsuperimposed, contiguous, mutually adhered layers.
 2. The collar ofclaim 1, being configured to prevent material of a conductive structuresecurable to the contact pad from contacting a region of a surface ofthe semiconductor device that surrounds the contact pad.
 3. The collarof claim 2, including an inner surface defining the aperture and whichis configured to be at least partially contacted by at least a portionof the conductive structure within the aperture.
 4. The collar of claim3, wherein the inner surface is configured to define a shape of at leasta portion of the conductive structure.
 5. The collar of claim 4, whereinthe inner surface is configured to define the conductive structure tohave a pillar shape.
 6. The collar of claim 4, wherein the inner surfaceis configured to define at least a base portion of the conductivestructure and to impart the conductive structure with a mushroom-likeshape.
 7. The collar of claim 4, wherein the inner surface is configuredto define the conductive structure to have a substantiallynonball-shaped configuration.
 8. The collar of claim 1, wherein at leastsome of the plurality of layers comprise photopolymer.
 9. A supportstructure for a discrete conductive structure, comprising: a pluralityof at least partially superimposed, mutually adhered, contiguous layerscomprising dielectric material; and a receptacle extending through eachof the plurality of at least partially superimposed, mutually adhered,contiguous material layers and configured to receive at least a portionof the discrete conductive structure.
 10. The support structure of claim9, wherein the plurality of at least partially superimposed, mutuallyadhered, contiguous material layers is configured to prevent material ofthe discrete conductive structure from extending laterally beyond aperiphery of the receptacle.
 11. The support structure of claim 9,wherein each of the plurality of at least partially superimposed,mutually adhered, contiguous material layers comprises photopolymer. 12.The support structure of claim 9, wherein the receptacle is configuredto contact at least a portion of an external surface of the discreteconductive structure.
 13. The support structure of claim 12, wherein theexternal surface is configured to define a shape of at least a portionof the discrete conductive structure.
 14. The support structure of claim9, wherein the receptacle is configured to receive substantially all ofthe discrete conductive structure.
 15. A form for at least a portion ofa discrete conductive structure, comprising: a body including aplurality of at least partially superimposed, mutually adhered,contiguous dielectric material layers; and a receptacle laterallyconfined by the body, the receptacle having a shape into which at leastthe portion of the discrete conductive structure is to be formed. 16.The form of claim 15, wherein each of the plurality of at leastpartially superimposed, mutually adhered, contiguous material layerscomprises photopolymer.
 17. The form of claim 15, wherein the receptacleopens to an end of the body to facilitate communication between thediscrete conductive structure and a portion of a contact around whichthe body is positioned.
 18. The form of claim 17, wherein the bodyprevents material of the portion of the discrete conductive structurefrom extending laterally beyond an outer periphery of the body.
 19. Theform of claim 17, wherein the body and the receptacle are configured tofacilitate alignment of the discrete conductive structure with thecontact.
 20. The form of claim 15, wherein the receptacle is configuredto form a shape of a substantial length of the discrete conductivestructure.